The Kimmel Cancer Center Transgenic and Knockout Mouse Facility is housed within the 11th floor Laboratory Animal Facility with a molecular laboratory and office on the 7th floor of the Bluemle Life Sciences Building (BLSB) and a dedicated cell culture laboratory on the 10th floor of the BLSB. The Facility is responsible for making transgenic mice carrying specific DNA constructs by microinjection of DNA into fertilized eggs. The Facility also produces mouse chimeras, using embryonic stem (ES) cells designed to carry gene knockouts or designer alterations that are the result of homologous recombination. Recently established gene targeting services provide the ability to manipulate the genome of ES cells to make designer alterations in any gene or region of interest. KCC investigators provide the DNA construct which is then electroporated into ES cells; the ES cells are subsequently subjected to selection, growth, colony isolation, molecular testing and expansion of selected ES colonies for injection into mouse embryos. Germplasm cryopreservation and embryo collection are being developed as additional services that will be offered to KCC investigators. Members of this facility also provide consultation for experimental design, mouse genetics, breeding strategies, cell culture techniques and colony maintenance procedures to KCC investigators and their staff.